AGM vs flooded charge time

[Sky_Boss]

Originally Posted by buckeyemike

My bank is the same size as yours 440 amp hours. so do you recall how long it takes your generator to bring you from a 60% SOC to a 90% SOC?

I don't have any exact numbers but I think it was about 2 hours or less.

Given my set up, it is really phenomenal how well it works. Because I haven't boondocked in situations where I should observe quiet time so I haven't done anything for planning around those hours. It is important that if you have quiet hours involved in your planning that you do a top off in time to keep your neighbors happy.

[OldToolmaker]

Originally Posted by Sky_Boss

Finally, how many batteries and their combined size will affect your recharge time. All things being equal, It takes about twice as long to recharge 880 AH worth of batteries from 50% SOC to 100% SOC as it takes to do the same for 440 AH batteries.

Sort of, kinda, not really.

Most intelligent battery charger - power supplies provide 14.4VDC for the bulk charge rate. The batteries accept all of that current that they need provided the power supply can deliver. In the beginning we were seriously cash strapped and I replaced the original harmonically regulated converter with a PD 9260. Practical experience shows that we could use an 80A or possible 100A PD power supply. But the PD isn't maxed out for more than say 45 minutes each charging cycle so the fuel saving doesn't cover the cost of an up-grade.

Bottom line here: The smart charger supplies the correct voltage. The battery bank accepts what current it needs up to the delivery limit of the smart charger. With a large enough smart charger all lead acid battery banks can be brought up to 80%-90% of full charge in four hours.

[Smitty77]

Originally Posted by Sky_Boss

AGMs CAN be charged with higher current than wet cells. Of course, the charger needs to be able to give them the extra current. If you have an ME inverter/charger (I have the MS 2812) you should see an AGM 1 (Lifeline Batteries) and and AGM 2 (all other AGMs) program which will take full control.

I just replaced my 4 Lifeline GP-4CT batteries with new ones. In the process I added a battery monitor kit (ME-BMK), ME-AGS and ME-ARC. I am very impressed with the charging performance of the system.

Let me toss out something else to consider. The time to charge any battery is directly related to how far you let them get depleted. Also, whether you are charging with solar power or a generator can influence the perception of how quickly a battery recharges.

For the most part you probably don't really care how quickly they charge if you are on shore power. If you are relying on solar or generator power you will care a bit more. Even then there are differences between Solar and generator power in how to better manage them.

As an example, if you have a good solar system and weather cooperates, you will charge your batteries up to 100% state of charge (SOC). With a generator only you will probably only charge to about 90% because the fuel it takes to get from 90% to 100% is not well spent.

These are all affected by how low you let your batteries get depleted. As a rule of thumb you seriously avoid discharging below 50% SOC. So, as an example, I have a total of 440 AHs at 12V. I need to recognize I really only have about 220 AHs that are useable without recharging. Yes, you can go further but how deep and how often you go below 50% SOC will determine how quickly you cause your batteries to deteriorate.

So...since I don't have solar and rely on a generator for my infrequent boon docking, I set my AGS to start charging at 60% SOC and shut down the generator when I reach 90% SOC. That protects my batteries and reduces the generator run time.

Finally, how many batteries and their combined size will affect your recharge time. All things being equal, It takes about twice as long to recharge 880 AH worth of batteries from 50% SOC to 100% SOC as it takes to do the same for 440 AH batteries.

Now...I realize I very generally answered a lot of questions you didn't ask. LOL These are just some things to consider before you get all hung up on recharge times.

Don - Great post, thanks for taking the time to share this info.

I'll add two more bits of input, suspect Don has one of them in his system:

1) AGM rated, including Lifeline, chargers. (Like the MExxxx series mentioned.), along with battery Temp Sensors.

Temp Sensors allow the more sophisticated chargers to provide the maximum safe charging times of your AGM's (And non AGM's). This can make a big difference in the results you see on timing to 100% SOC.

2) Same comment in regards the combo of Solar Panels and Controllers. A larger capacity set of SP's, with a Temp Sensor fed Controller, properly set for your specific AGM's - will maximize the fast safe charging times to 100% SOC.

We too have the MS2812. We also have 1200W of 48V High Efficiency Solar Panels, feeding down to the battery bank with the MidNite Classic 150. Adding the WhzBangJr (Think that is what it is called.) feature of the MidNite controller, is worth the extra funds.

We have X's 4 L16 Lifelines, for 800AH of house battery. We very seldom need to plug our coach into house power, as the SP's keep us fully charged.

For example, tailgated before the NFL Charger/Denver game on Sunday. Had a crock pot running, used the microwave off and on, made two pots of coffee, stereo and TV were on. We had a 100% SOC when we setup at 9:00AM, we dipped down to 95% SOC at around 10:30AM (After much of thus heavier usage.) but by the time we left at 12:15PM to head into the game, the SP's had us back up to 100% SOC.

For those that boon dock, having excess capacity SP's, and Controllers sophisticated enough to provide maximum safe charging, can make the need to run the generator much less. (We run for AC if needed, and for any Convection Oven usage of over 20 mins. (Though if this at dinner time, I will run the generator for this Oven usage, as we have less time for the SP's to bring things back up. If at lunchtime, I don't run the generator for under 20 mins, and we are at 100% SOC before the sun is down.)

As mentioned, lots of variables, and yes - you can spend some good coin! I looked at this rig having a 10-15 year life usage ahead, so I amortized the costs of the modifications we make over this enjoyment of usage ratio!

Others mileage and opinions will vary - and that is OK!!
Best to all,
Smitty

[Sky_Boss]

Smitty,

I would really like to have a system like that with only 440 AHs of battery storage I'm not certain it is worth it. I would have to do some major reworking of may battery placement and cables to do it right. I was about 1" too short in my battery bay to upgrade to GP-6CT batteries to get me up to 660 AHs. SIGH!

For my needs that would have been sufficient to keep me happy for up the 12 solid hours of boon docking. I really don't plan to do a lot of serious boon docking in the future.

[wa8yxm]

FACT: From many other threads I know there are folks around here who have the time and tools to do charge studies.

I have seen some showing for example Progressive Dynamics, v/s Xantrex V/S Iota V/S other converters.

How about a comparison between a couple of brand new LIFELINE AGM's v/s say a pair of Trojan's DEKA, or Johnson Control Flooded, using the SAME converters,, Say a 60 amp Progressive Dynamics or IOTA.

[Reed Cundiff]

We had AGMs with our first rig. We figured out, as one of the posters above noted, that if we were way down in charge, it was best to run the generator the first thing in the morning, and then let solar take it through absorb. Have a lot more panels and different batteries so things are simpler now.

Reed and Elaine

[joes2901]

My setup is similar to Smitty77's, but I am using an Outback solar controller for 765 watts of solar power. I only like to boondock and during the summer the generator only runs if there are 2 back to back cloudy days. Then if the SOC is under 65% and after 8:00 AM and the sun is shining it takes about 1.5 hours to get back to 90%. The Outback will match the voltage to the MS2812's and add about 40 Amps. for 165 Amps. to the battery bank which gives the reduction in generator run time. At the end of the daylight the batteries are usually at 100%.

I turn the inverter on at home to begin making ice cubes and off when I return home. In the winter there is about half of the summer solar power available so you want to double the battery bank and solar panel sizes if you use your RV in the Winter months, like at Quartzsite, AZ.

[Tony Lee]

Those assuring us that AGM batteries can be equalised might give us some details.

For instance, do all AGM manufacturers recommend equalising?
Which do and which specifically recommend against it.
Is the equalising sequence - times and voltages - the same as that used for conventional flooded LA batteries?
How does one determine that the batteries are "a little down in capacity" and so should be equalised (if that is the manufacturer's criteria)
What precautions should be followed.
Etc etc etc

Unless the recommendations are universal and fully detailed, some members might get a little annoyed if they follow advice and end up wrecking perfectly good batteries.

[OldToolmaker]

Originally Posted by Tony Lee

Which do and which specifically recommend against it.
Is the equalizing sequence - times and voltages - the same as that used for conventional flooded LA batteries?

AGM translates to Absorbed Glass Mat

Gel is easier, the electrolyte is gelled to keep it from spilling and makes it possible to mount the battery other than upright.

VRLA means Valve Regulated Lead Acid and applies to both types of batteries.

They are all lead acid batteries.

If you charge a Gell cell battery with too much voltage a bubble will form between the plate and the gelled electrolyte.

If you do the same to an AGM battery the battery will vent and become a little drier inside. An AGM battery won't spill and because it only has 95% of the electrolyte needed it can't be over charged in a way that causes plate corrosion.

Equalizing charges? Well you won't void your warranty if that's what the manufacturer of your battery recommends.

[jauguston]

Something else to consider when talking about recharging is recharge voltage. For the longest time 14.4v has been suggested as the maximum voltage that should be used to recharge 12v battery banks. Now that is not necessarily true. Many battery manufacturers now recommend 14.8v as the proper charge voltage to be able to attain 100% SOC. My Full River 6v AGM batteries have a maximum recommended charge voltage for a 12v pair of 14.9v. My Magnum has a 14.8v setting I use. My Blue Sky solar controller also has a 14.8v setting I also use.

Jim

[buckeyemike]

Update: I have since the first post, replaced my flooded bank with lifeline batteries and in their literature they claim that agms have a 20% faster charge time

[wa8yxm]

Old Toolmaker, AGM also do not come with a "This Side UP" they have all the advantages of GEL and none of the disadvantages of GEL,, Gel batteries are a real pain, you really have to baby those puppies. What do I mean by that.

Charge them too fast: Well you basically can not charge Lifeline AGM's too fast, you do not have enough converter to do that. But you can charge a same size GEL too fast and if you do.. Replace it.

For buckymike.. yes, you can recharge them faster but you need a faster charger to do it

I am still waiting on a comparison of charge times with the following conditions:

Same amount of batteries (Example, both banks 230 or 460 amp hours)
SAME CONVERTER.
Equlize... Yes, AGM's can be equalized when/if needed,, GEL.. You can do that once, then you replace it.

They are the fussiest battery made.

[dons2346]

"I am still waiting on a comparison of charge times with the following conditions:

Same amount of batteries (Example, both banks 230 or 460 amp hours)
SAME CONVERTER."

Cough up the bux to purchase the inverters and batteries and we can get the show on the road.

[wa8yxm]

That shold not be necessary... If someone records the times to charge a new set of say Interstate Flooded wet... then a decade from now puts in Lifelines.... and again records.

I'm willing to wait.